CN112516615A - Device and method for crystallization purification - Google Patents
Device and method for crystallization purification Download PDFInfo
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- CN112516615A CN112516615A CN201910889144.XA CN201910889144A CN112516615A CN 112516615 A CN112516615 A CN 112516615A CN 201910889144 A CN201910889144 A CN 201910889144A CN 112516615 A CN112516615 A CN 112516615A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
- B01D9/0004—Crystallisation cooling by heat exchange
- B01D9/0013—Crystallisation cooling by heat exchange by indirect heat exchange
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D317/00—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms
- C07D317/08—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3
- C07D317/10—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3 not condensed with other rings
- C07D317/32—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3 not condensed with other rings with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
- C07D317/34—Oxygen atoms
- C07D317/36—Alkylene carbonates; Substituted alkylene carbonates
- C07D317/38—Ethylene carbonate
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
- B01D2009/0086—Processes or apparatus therefor
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Abstract
The invention relates to a device and a method for purifying crystals. The device comprises a shell, wherein the top of the shell is provided with a cold/hot agent inlet, the bottom of the shell is provided with a cold/hot agent outlet, two sides of the shell are respectively provided with a material inlet and a material outlet, and the horizontal position of the material inlet is higher than that of the material outlet; the heat exchange tube and the liquid distributor are arranged in the shell, and the material distributor is arranged at the bottom of the shell upper end socket; the top of the heat exchange tube is connected with the liquid distributor, the bottom of the heat exchange tube is connected with the outlet of the cold/hot agent through the lower shell end socket, the outer wall surface of the heat exchange tube has roughness, and meanwhile, the heat exchange tube is provided with a supporting piece. The ethylene carbonate product with the purity of more than or equal to 99.99 percent can be obtained by the method for crystallizing and purifying the ethylene carbonate by utilizing the device.
Description
Technical Field
The invention belongs to the field of purification of ethylene carbonate, and particularly relates to a device and a method for crystallization purification.
Background
Ethylene carbonate (EC, C)3H4O3And CAS number: 96-49-1), which is a high boiling point solvent and organic synthesis intermediate with excellent performance, and is widely used in the fields of textile printing and dyeing, polymer synthesis, electrochemistry, medicine and the like, wherein the refined EC is one of the raw materials for producing high-energy lithium ion battery electrolyte and has high added value, so that the refined EC of the power battery grade has a wide development prospect obviously along with the rapid development of the power lithium battery market.
The traditional EC production method is a phosgene method, namely ethylene glycol and phosgene are directly reacted to generate the ethylene glycol-phosgene, but the traditional EC production method has the defects of long process flow, low yield, high cost, high phosgene toxicity, serious pollution and the like, and is basically eliminated at present; the transesterification method using diethyl carbonate and ethylene glycol as raw materials has the advantages that although the steps are simple, the raw materials are expensive, and the tin catalyst has high toxicity and no practical industrial application value; at present, carbon dioxide (CO) is generally adopted2) And Ethylene Oxide (EO) are taken as raw materials to prepare EC through direct esterification, so that economic benefits are improved, and a new method for chemically utilizing CO is provided while attention is continuously paid to energy and environmental protection in various countries in the world2The method has the advantages of resource, development of a new way of carbon-chemical industry, obvious social benefit, and high efficiency, greenness and environmental protection.
Because the performance of the lithium ion battery depends on the performance and the preparation process of the battery composition materials to a great extent, for example, a small amount of water, alcohol and acid in the electrolyte solvent can cause the reduction of the specific capacity, the conductivity, the cycle efficiency and the like of the lithium ion battery, and even accelerate the deterioration of the electrolyte, in the production process of the power lithium ion battery, strict requirements are made on the purity of the electrolyte solvent, and the EC purity is generally required to reach 99.99%.
At EO and CO2The reaction product of (A) contains a small amount of ethylene glycol, diethylene glycol, water, unreacted EO, and even unreacted EO, in addition to the target product ECMay contain catalyst residues, etc. At present, the purification method of battery-grade EC in an industrial device is mainly rectification purification, i.e. EC with purity of more than 90% obtained by crude distillation is further rectified, as described in CN 106588862, however, in the rectification purification process, on one hand, if the temperature in the rectification process is high and the time is long, the polymerization and decomposition of EC are easily caused, and even if there is catalyst residue in the raw material, more decomposition of EC is caused, therefore, in order to ensure the product purity, the temperature in the rectification process needs to be reduced, at this time, a very high vacuum degree (system pressure about 5KPa, absolute pressure) is needed, high requirements are required for both equipment and operation, and the equipment and operation costs are also high; on the other hand, because the purity requirement of the battery grade EC is very high, the reflux ratio of the rectification process is very high, and the energy consumption is very high. Thus, while purification by distillation is currently the primary method of cell-grade EC production, it is not the most economically desirable method of production and improvements are needed.
By adopting a crystallization separation method, CN101400667B proposes a purification method of feeding an EC solution into a washing tower for countercurrent contact after crystallization, but it is known that a crystal bed layer in the washing tower is not easy to be stable and has high requirements on the operation of equipment.
In addition to conventional rectification and crystallization methods, CN201010598710.0 proposes a molecular sieve adsorption method to dehydrate and remove ethylene glycol from EC material with a purity of about 99.9%, but the molecular sieve is used in a large amount, and adsorbs EC while adsorbing ethylene glycol and water, resulting in EC loss and yield reduction, and at the same time, the molecular sieve is easy to be adsorbed and saturated, resulting in EC material throughput reduction, and further considering molecular sieve regeneration in industrial application is not an optimal separation method; CN201510404219.2 proposes to perform a glycol removal treatment by complexing a complex with ethylene glycol as an impurity in industrial EC to generate an insoluble metal salt complex and then performing further filtration and separation, but the introduction of the complex can also cause the appearance of new impurities, and brings a new separation problem for the purification of battery-grade EC products with extremely high purity requirements. However, it should be noted that the above processes are all for post-treatment of high purity EC with purity up to 99% or more to further reduce the content of some impurities, such as ethylene glycol and water, but do not consider the prior purification of EC or the design and optimization of the overall process, such as the separation of EC reaction products based on Ethylene Oxide (EO) esterification, and are not suitable for the overall industrial application of EC.
Therefore, compared with the conventional rectification purification method, or other separation methods, or combined separation methods, the direct crystallization separation purification method for the ethylene carbonate, particularly the power battery grade EC is developed, so that the separation energy consumption can be remarkably reduced, the equipment and operation can be greatly simplified, and the direct crystallization separation purification method for the ethylene carbonate, particularly the power battery grade EC can be directly used for industrial production of the power battery grade EC and has obvious advantages.
Disclosure of Invention
The invention provides a device and a method for crystallizing and purifying ethylene carbonate aiming at the technical problems of high energy consumption, low product purity and the like in the process of separating and purifying ethylene carbonate in the prior art.
To this end, the present invention provides, in a first aspect, an apparatus for purification by crystallization, comprising:
the device comprises a shell, wherein the top of the shell is provided with a cold/hot agent inlet, the bottom of the shell is provided with a cold/hot agent outlet, two sides of the shell are respectively provided with a material inlet and a material outlet, and the horizontal position of the material inlet is higher than that of the material outlet;
the heat exchange tube and the liquid distributor are arranged in the shell, and the liquid distributor is arranged at the bottom of the shell upper end socket; the top of the heat exchange tube is connected with the liquid distributor, the bottom of the heat exchange tube is connected with the outlet of the cold/hot agent through the lower shell end socket, the outer wall surface of the heat exchange tube has roughness, and meanwhile, the heat exchange tube is provided with a supporting piece.
The main structure of the device is a vertical shell-and-tube crystallizer, and the device is also provided with a pressure and temperature measuring port for detecting the temperature and the pressure in the device.
In some embodiments of the invention, the surface roughness of the outer wall surface of the heat exchange tube is 3.2-50, preferably 6.3-25, so as to facilitate the precipitation of crystals from the outer surface of the heat exchange tube.
In the invention, the supporting pieces are arranged on the outer wall surface of the heat exchange tube and are uniformly or non-uniformly distributed on the outer wall surface of the heat exchange tube, so that the crystallization and sweating processes are ensured, particularly the sweating process is ensured to be carried out at a higher sweating temperature and a longer sweating time, and the product purity is improved. The structure of the supporting piece is net-shaped, rod-shaped or sheet-shaped. Preferably, the distance between each layer of the supporting pieces is 0.5-5 times of the diameter of the device, and more preferably, the distance between each layer of the supporting pieces is 1-3 times of the diameter of the device.
In other embodiments of the present invention, the number of the heat exchange pipes is two or more. The number of the heat exchange tubes is not definitely limited, and the corresponding number of the heat exchange tubes can be set according to actual needs.
In some embodiments of the invention, an overflow weir is arranged above the liquid distributor or an extension pipe is arranged below the liquid distributor, and the extension pipe is positioned in the heat exchange pipe; after the cold/hot agent is uniformly distributed by the liquid distributor, the cold/hot agent enters the heat exchange tube through the overflow weir or the extension tube and flows along the inner wall surface of the heat exchange tube, so that the heat exchange efficiency of one side of the cold/hot agent is improved, the heat exchange efficiency of the crystallization process is improved, the separation of impurities in the crystallization process is reduced, the heat exchange efficiency of the sweating process is improved, the mother liquid contained in crystals is separated out more easily, and the product quality is improved. Preferably, the extension tube arranged below the liquid distributor is in the shape of a cone, a spiral, a sawtooth or the like.
In other embodiments of the present invention, the material inlet and the exterior of the heat exchange tube are provided with extension tubes, and the raw material containing ethylene carbonate flows along the outer wall surface of the heat exchange tube after passing through the material inlet and the extension tubes disposed on the exterior of the heat exchange tube, so that the heat exchange efficiency on one side of the material is improved, the separation of impurities during the crystallization process is reduced, the bulk density of crystals is increased, and the purity of the product is improved. The shape of the extension tube arranged at the material inlet and the outer part of the heat exchange tube is inverted cone, spiral or zigzag and the like.
In some embodiments of the invention, the apparatus further comprises a nitrogen inlet for introducing nitrogen into the apparatus, the nitrogen inlet being located on a side of the housing.
In some embodiments of the invention, the apparatus further comprises an external material circulation pump, an inlet of the external material circulation pump is connected to the material outlet through a pipeline, and an outlet of the external material circulation pump is connected to the material inlet through a pipeline. The external feed circulation pump may be used to pump material discharged from the feed outlet back to the feed inlet and maintain flow of the ethylene carbonate feed.
In other embodiments of the present invention, the apparatus further comprises an external temperature control system containing a cold/hot agent, the outlet of which is connected to the cold/hot agent inlet via a conduit, and the inlet of which is connected to the cold/hot agent outlet via a conduit. The external temperature control system is used to control the temperature of the device.
In a second aspect, the present invention provides a method for purifying ethylene carbonate by crystallization using the apparatus according to the first aspect, comprising the following steps:
s1, introducing a raw material containing vinyl carbonate into the device through a material inlet of the device, and flowing along the outer wall surface of the heat exchange tube through the material inlet and an extension tube arranged outside the heat exchange tube;
s2, introducing a refrigerant into the device through a cold/hot agent inlet, distributing the refrigerant through a liquid distributor, then entering the heat exchange tube along an overflow weir arranged above the liquid distributor or an extension tube arranged below the liquid distributor, flowing along the inner wall surface of the heat exchange tube, controlling the temperature through an external temperature control system, crystallizing the ethylene carbonate in the raw material on the outer wall of the heat exchange tube, and discharging crystallization mother liquor after crystallization is finished;
s3, introducing a hot agent into the device through the cold/hot agent inlet, after the hot agent is distributed by the liquid distributor, entering the heat exchange tube along an overflow weir arranged above the liquid distributor or an extension tube arranged below the liquid distributor, flowing along the inner wall surface of the heat exchange tube, controlling the temperature through an external temperature control system, sweating the crystal on the outer wall of the heat exchange tube, discharging sweat from the material outlet of the device, wherein the residual crystal on the outer wall of the heat exchange tube is the purified ethylene carbonate product.
According to the invention, with the reduction of the temperature of the refrigerant and the direct and efficient heat exchange between the material and the refrigerant on the wall surface, the ethylene carbonate crystals are gradually crystallized and precipitated on the outer wall of the tube array.
In some embodiments of the invention, the method further comprises: and after the sweat is discharged, the temperature of the heating agent is continuously raised, the residual crystals on the outer wall of the heat exchange tube are melted in one step and then flow out from the material outlet, and the obtained purified ethylene carbonate product is collected.
In the method, the ethylene carbonate is separated and purified by adopting a melt crystallization method, and the crystallized crystals and the mother liquor can be directly separated without introducing a third substance, so that the method has the characteristics of simple process steps, high product purity, low energy consumption and the like.
In some embodiments of the invention, the cooling rate in the crystallization process is 0.01-0.15 ℃/min, the crystallization end point temperature is 15-25 ℃, and the constant temperature time at the crystallization end point temperature is not less than 30 min.
In other embodiments of the invention, the temperature rise rate in the sweating process is 0.01-0.1 ℃/min, the sweating end point temperature is 36.5-38 ℃, and the constant temperature time of the sweating end point temperature is not less than 30 min.
In some embodiments of the invention, the formation of crystals during crystallization is natural crystallization or crystallization is initiated by the addition of seed crystals. No seed crystal is added in the natural crystallization process, and the operation is relatively simple. And the crystallization process is initiated, which is beneficial to controlling the supersaturation degree of the crystallization process and improving the purity of the crystal product.
In some preferred embodiments of the present invention, the seed crystal is a magma solution of ethylene carbonate having a solid mass content of not more than 20%; preferably, the adding temperature of the seed crystal is 34-36 ℃.
In some embodiments of the present invention, in order to improve the heat exchange efficiency of the inner wall surface of the tube array, the external material circulation pump is intermittently started after the crystallization process is started, or the external material circulation pump is continuously started, and the raw material containing the vinyl carbonate is kept flowing slowly until the crystallization process is finished. Therefore, the crystallization of the ethylene carbonate can be accelerated, the crystallization rate can be improved, and the mother liquor entrainment in the ethylene carbonate crystallization process can be reduced, so that the yield and the purity of the product can be improved.
In other embodiments of the present invention, the method is performed under nitrogen gas sealing. Because the ethylene carbonate is particularly easy to absorb moisture in the air, the ethylene carbonate can be prevented from contacting the air in the whole purification process including raw material feeding, crystal crystallization and sweating, material storage and the like by adopting a nitrogen sealing mode, the ethylene carbonate is prevented from being decomposed and the purity of the ethylene carbonate is prevented from being reduced due to the introduction of moisture in the air, and the separation and purification effects are further ensured.
In some embodiments of the present invention, the ethylene carbonate content of the ethylene carbonate-containing feedstock is greater than or equal to 90% by mass. The raw material containing the ethylene carbonate can be a direct reaction product or a raw material rich in the ethylene carbonate with the mass content of the ethylene carbonate of which the low-concentration reaction product is primarily purified being more than or equal to 90 percent. Other ethylene carbonate materials with the mass content of more than or equal to 90 percent can also be used. Under the influence of various factors such as a synthesis method, the types of catalysts, different process conditions and the like, the concentration of the ethylene carbonate in the ethylene carbonate reaction product is different, the purity of some ethylene carbonate reaction products is higher than 98%, the purity of some ethylene carbonate reaction products is lower than 90%, and the reaction product with the purity of lower than 90% is subjected to preliminary purification through conventional separation processes such as reduced pressure rectification, single-stage melt crystallization or membrane separation and the like, and then the device and the method are adopted for further separation and purification to obtain a high-purity ethylene carbonate product; meanwhile, compared with a direct rectification separation and purification method which needs high vacuum and high reflux ratio, the method has the advantages of mild separation conditions and obviously reduced energy consumption.
Based on the fact that the fusion latent heat of the ethylene carbonate is obviously lower than the vaporization latent heat of the ethylene carbonate, compared with the traditional rectification and purification method, the method provided by the invention can obviously reduce the energy consumption in the separation process, and meanwhile, the process is milder.
Compared with other crystallization separation processes, the method disclosed by the invention is innovative on the adopted purification device, on one hand, the ethylene carbonate raw material and the cold/heat agent are directly and quickly contacted on a contact surface (namely the inner wall surface and the outer wall surface of the heat exchange tube) by additionally arranging the overflow weir and/or the extension tube at the inner part and the outer part of the heat exchange tube and additionally arranging the external circulating pump, so that the heat exchange efficiency in the crystallization and sweating processes is greatly improved, the precipitation of impurities in the crystallization process is favorably reduced, the precipitation of mother liquor mixed in crystals in the sweating process is favorably accelerated, and the purity of an EC product is improved. On the other hand, because the ethylene carbonate crystal is crystallized on the outer wall surface of the heat exchange tube, the wall surface of the ethylene carbonate crystal has certain roughness and the supporting piece is arranged to be beneficial to the crystal attachment in the crystallization and sweating process, and particularly, the separation effect between the mother solution seeped out of the crystal and the remaining sweating crystal in the sweating process is improved, so that the sweating process of the crystal can be carried out at higher sweating temperature and longer sweating time, more impurities attached or carried in the crystal layer are precipitated, the sweating process is ensured, the sweating effect is improved, the purity of the EC product is improved, and a better technical effect is obtained.
The method can obtain the ethylene carbonate product with the purity of more than or equal to 99.99 percent, and the purity can meet the product purity requirements of the general ethylene carbonate industry and other battery grades, particularly the power battery grade ethylene carbonate industry; in addition, the method can be further combined with separation methods such as adsorption, membrane separation and the like so as to further remove impurities such as ethylene glycol, water and the like in the ethylene carbonate crystal product and continuously improve the product quality. Meanwhile, mother liquor and sweat generated in the crystallization and sweating processes can also be continuously subjected to secondary and multistage crystallization and sweating so as to further improve the product yield of the ethylene carbonate.
Drawings
The invention will be further explained with reference to the drawings.
FIG. 1 is a schematic structural diagram of an apparatus for crystallization and purification of ethylene carbonate according to the present invention.
FIG. 2 is a schematic structural diagram of the apparatus for crystallization and purification of ethylene carbonate according to the present invention.
FIG. 3 is a partial schematic view of an extension tube in accordance with the present invention; wherein (a) and (b) are schematic diagrams of extension tubes below the liquid distributor (inside the heat exchange tube), and (c) is a schematic diagram of extension tubes at the material inlet and outside the heat exchange tube.
Wherein the reference numerals in the figures have the meaning: 1, a shell of a crystallization and purification device; 2, exchanging a heat pipe; 3 a liquid distributor; 4, an overflow weir; 4a an extension tube arranged below the liquid distributor; 5, an extension pipe is arranged at the material inlet and outside the heat exchange pipe; 6 a support member; 7, a material inlet; 8, a material outlet; 9 a cold/hot agent inlet; 10 cold/hot agent outlet; 11 a nitrogen inlet; 12 a temperature measuring port; 13 a pressure measurement port; 14 external material circulating pump; 15 an external temperature control system; 16 a tapered extension tube; 17 a zigzag extension tube; 18 an inverted conical extension tube.
Detailed Description
In order that the present invention may be more readily understood, the following detailed description will proceed with reference being made to examples, which are intended to be illustrative only and are not intended to limit the scope of the invention. The starting materials or components used in the present invention may be commercially or conventionally prepared unless otherwise specified.
Example 1
The crystallization purification device shown in fig. 1 is adopted, an overflow weir is arranged above the liquid distributor, and a zigzag extension pipe is arranged at the side material inlet and outside the heat exchange pipe. The surface roughness of the outer wall surface of the heat exchange tube is 25. The supporting piece outside the heat exchange tube is a rod-shaped stainless steel tube cluster inclined downwards at 45 degrees, and the whole height is flush with the liquid level in the device.
Raw materials which comprise 90.15 percent of ethylene carbonate, 6.23 percent of ethylene glycol and 3.62 percent of other EC by weight percentage enter from a side material inlet after being preheated and melted, enter the device through the material inlet and a guide pipe outside the heat exchange pipe, and flow downwards along the outer wall surface of the heat exchange pipe. The cold agent enters from the cold/hot agent inlet, enters the heat exchange tube through the liquid distributor and the overflow weir above the liquid distributor, and flows downwards along the inner wall surface.
Carrying out program temperature control through an external temperature control system to enable the ethylene carbonate material to naturally crystallize along the outer wall surface of the heat exchange tube, wherein the cooling rate is 0.01 ℃/min, the crystallization end point temperature is 15 ℃, and the temperature is kept for 60min at the crystallization end point temperature; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, allowing a hot agent to enter from a cold/hot agent inlet, allowing the hot agent to flow downwards along the inner wall surface of the heat exchange tube through an overflow weir, sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature raising rate is 0.01 ℃/min, the sweating end point temperature is 36.5 ℃, the constant temperature is kept at the sweating end point temperature for 60min, and the sweat is discharged through the material outlet simultaneously in the sweating process; after sweating was stopped, the temperature of the thermite was increased continuously, the residual crystals outside the heat exchange tubes were melted and collected, and the final EC product purity was 99.993%.
Example 2
With the crystallization purification apparatus shown in fig. 1, an overflow weir is provided above the liquid distributor, and an inverted conical extension tube is provided at the inlet of the side material inlet and outside the heat exchange tube, as shown in fig. 3 (c). The surface roughness of the outer wall surface of the heat exchange tube is 25. The supporting piece outside the heat exchange tube is a rod-shaped stainless steel tube cluster inclined downwards at 45 degrees, and the whole height is flush with the liquid level in the device.
Raw materials which comprise 90.15 percent of ethylene carbonate, 6.23 percent of ethylene glycol and 3.62 percent of other EC by weight percentage enter from a side material inlet after being preheated and melted, enter the device through the material inlet and a guide pipe outside the heat exchange pipe, and flow downwards along the outer wall surface of the heat exchange pipe. The cold agent enters from the cold/hot agent inlet, enters the heat exchange tube through the liquid distributor and the overflow weir above the liquid distributor, and flows downwards along the inner wall surface.
Carrying out program temperature control through an external temperature control system to enable the ethylene carbonate material to naturally crystallize along the outer wall surface of the heat exchange tube, wherein the cooling rate is 0.01 ℃/min, the crystallization end point temperature is 15 ℃, and the temperature is kept for 60min at the crystallization end point temperature; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, allowing a hot agent to enter from a cold/hot agent inlet, allowing the hot agent to flow downwards along the inner wall surface of the heat exchange tube through an overflow weir, sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature raising rate is 0.01 ℃/min, the sweating end point temperature is 36.5 ℃, the constant temperature is kept at the sweating end point temperature for 60min, and the sweat is discharged through the material outlet simultaneously in the sweating process; after sweating was stopped, the temperature of the thermite was increased continuously, the residual crystals outside the heat exchange tubes were melted and collected, and the final EC product purity was 99.993%.
Example 3
By adopting the crystallization purification device shown in fig. 1, an overflow weir is arranged above the liquid distributor, and an inverted cone-shaped extension tube is arranged at the side material inlet and outside the heat exchange tube, as shown in (c) of fig. 3. The surface roughness of the outer wall surface of the heat exchange tube is 3.2. The supporting piece outside the heat exchange tube is a rod-shaped stainless steel tube cluster inclined downwards at 45 degrees, and the whole height is flush with the liquid level in the device.
Raw materials which comprise 90.15 percent of ethylene carbonate, 6.23 percent of ethylene glycol and 3.62 percent of other EC by weight percentage enter from a side material inlet after being preheated and melted, enter the device through the material inlet and a guide pipe outside the heat exchange pipe, and flow downwards along the outer wall surface of the heat exchange pipe. The cold agent enters from the cold/hot agent inlet, enters the heat exchange tube through the liquid distributor and the overflow weir above the liquid distributor, and flows downwards along the inner wall surface.
Carrying out program temperature control through an external temperature control system to enable the ethylene carbonate material to naturally crystallize along the outer wall surface of the heat exchange tube, wherein the cooling rate is 0.01 ℃/min, the crystallization end point temperature is 15 ℃, and the temperature is kept for 60min at the crystallization end point temperature; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, allowing a hot agent to enter from a cold/hot agent inlet, allowing the hot agent to flow downwards along the inner wall surface of the heat exchange tube through an overflow weir, sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature raising rate is 0.01 ℃/min, the sweating end point temperature is 36.5 ℃, the constant temperature is kept at the sweating end point temperature for 60min, and the sweat is discharged through the material outlet simultaneously in the sweating process; after sweating was stopped, the temperature of the thermite was increased continuously, and the residual crystals outside the heat exchange tubes were melted and collected, with a final EC product purity of 99.989%.
Example 4
By adopting the crystallization purification device shown in fig. 1, an overflow weir is arranged above the liquid distributor, and an inverted cone-shaped extension tube is arranged at the side material inlet and outside the heat exchange tube, as shown in (c) of fig. 3. The surface roughness of the outer wall surface of the heat exchange tube is 50. The supporting piece outside the heat exchange tube is a rod-shaped stainless steel tube cluster inclined downwards at 45 degrees, and the whole height is flush with the liquid level in the device.
Raw materials which comprise 90.15 percent of ethylene carbonate, 6.23 percent of ethylene glycol and 3.62 percent of other EC by weight percentage enter from a side material inlet after being preheated and melted, enter the device through the material inlet and a guide pipe outside the heat exchange pipe, and flow downwards along the outer wall surface of the heat exchange pipe. The cold agent enters from the cold/hot agent inlet, enters the heat exchange tube through the liquid distributor and the overflow weir above the liquid distributor, and flows downwards along the inner wall surface.
Carrying out program temperature control through an external temperature control system to enable the ethylene carbonate material to naturally crystallize along the outer wall surface of the heat exchange tube, wherein the cooling rate is 0.01 ℃/min, the crystallization end point temperature is 15 ℃, and the temperature is kept for 60min at the crystallization end point temperature; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, allowing a hot agent to enter from a cold/hot agent inlet, allowing the hot agent to flow downwards along the inner wall surface of the heat exchange tube through an overflow weir, sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature raising rate is 0.01 ℃/min, the sweating end point temperature is 36.5 ℃, the constant temperature is kept at the sweating end point temperature for 60min, and the sweat is discharged through the material outlet simultaneously in the sweating process; after sweating ceased, the thermite temperature was continued to be raised and the residual crystals outside the heat exchange tubes were melted and collected to a final EC product purity of 99.992%.
Example 5
By adopting the crystallization purification device shown in fig. 1, an overflow weir is arranged above the liquid distributor, and an inverted cone-shaped extension tube is arranged at the side material inlet and outside the heat exchange tube, as shown in (c) of fig. 3. The surface roughness of the outer wall surface of the heat exchange tube is 6.3. The supporting piece outside the heat exchange tube is a plurality of layers of stainless steel wire meshes, and the distance between every two layers is 0.5 times of the diameter of the device.
Raw materials which comprise 95.27 percent of ethylene carbonate, 2.93 percent of ethylene glycol and 1.80 percent of other EC by weight percentage enter from a side material inlet after being preheated and melted, enter the device through a material inlet and a guide pipe outside the heat exchange pipe, and flow downwards along the outer wall surface of the heat exchange pipe. The cold agent enters from the cold/hot agent inlet, enters the heat exchange tube through the liquid distributor and the overflow weir above the liquid distributor, and flows downwards along the inner wall surface.
Carrying out program temperature control through an external temperature control system to enable the ethylene carbonate material to naturally crystallize along the outer wall surface of the heat exchange tube, wherein the cooling rate is 0.05 ℃/min, the crystallization end point temperature is 20 ℃, and the temperature is kept for 60min at the crystallization end point temperature; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, allowing a hot agent to enter from a cold/hot agent inlet, allowing the hot agent to flow downwards along the inner wall surface of the heat exchange tube through an overflow weir, sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature raising rate is 0.025 ℃/min, the sweating end point temperature is 36.8 ℃, the constant temperature is kept at the sweating end point temperature for 60min, and the sweat is discharged through the material outlet simultaneously in the sweating process; after sweating was stopped, the thermite temperature was continued to be raised, and the residual crystals outside the heat exchange tubes were melted and collected, resulting in a final EC product purity of 99.995%.
Example 6
By adopting the crystallization purification device shown in fig. 1, an overflow weir is arranged above the liquid distributor, and an inverted cone-shaped extension tube is arranged at the side material inlet and outside the heat exchange tube, as shown in (c) of fig. 3. The surface roughness of the outer wall surface of the heat exchange tube is 6.3. The supporting piece outside the heat exchange tube is a plurality of layers of stainless steel wire meshes, and the distance between every two layers is 5 times of the diameter of the device.
Raw materials containing EC, which comprise 95.27 percent of ethylene carbonate, 2.93 percent of ethylene glycol and 1.80 percent of other raw materials by weight percent, enter from a side material inlet after being preheated and melted, enter the device through the material inlet and a stretching tube outside the heat exchange tube, and flow downwards along the outer wall surface of the heat exchange tube. The cold agent enters from the cold/hot agent inlet, enters the heat exchange tube through the liquid distributor and the overflow weir above the liquid distributor, and flows downwards along the inner wall surface.
Carrying out program temperature control through an external temperature control system to enable the ethylene carbonate material to naturally crystallize along the outer wall surface of the heat exchange tube, wherein the cooling rate is 0.05 ℃/min, the crystallization end point temperature is 20 ℃, and the temperature is kept for 60min at the crystallization end point temperature; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, allowing a hot agent to enter from a cold/hot agent inlet, allowing the hot agent to flow downwards along the inner wall surface of the heat exchange tube through an overflow weir, sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature raising rate is 0.025 ℃/min, the sweating end point temperature is 36.8 ℃, the constant temperature is kept at the sweating end point temperature for 60min, and the sweat is discharged through the material outlet simultaneously in the sweating process; after sweating ceased, the thermite temperature was continued to be raised and the residual crystals outside the heat exchange tubes were melted and collected to a final EC product purity of 99.992%.
Example 7
The crystallization purification device shown in fig. 1 is adopted, an overflow weir is arranged above the liquid distributor, and a spiral extension pipe is arranged at the side material inlet and outside the heat exchange pipe. The surface roughness of the outer wall surface of the heat exchange tube is 25. The supporting piece outside the heat exchange tube is a stainless steel sheet layer with the direction of 60 degrees and the downward inclination, and the distance between every two layers is 1 time of the diameter of the device.
Raw materials which comprise 99.07 percent of ethylene carbonate, 0.56 percent of ethylene glycol and 0.37 percent of other EC by weight percentage are preheated and melted, enter from a side material inlet, enter the device through a material inlet and a stretching tube outside the heat exchange tube, and flow downwards along the outer wall surface of the heat exchange tube. The cold agent enters from the cold/hot agent inlet, enters the heat exchange tube through the liquid distributor and the overflow weir above the liquid distributor, and flows downwards along the inner wall surface.
Carrying out program temperature control through an external temperature control system to enable the ethylene carbonate material to naturally crystallize along the outer wall surface of the heat exchange tube, wherein the cooling rate is 0.10 ℃/min, the crystallization end point temperature is 22.5 ℃, and the constant temperature is kept for 45min at the end point temperature; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, allowing a hot agent to enter from a cold/hot agent inlet, allowing the hot agent to flow downwards along the inner wall surface of the heat exchange tube through an overflow weir, sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature rise rate is 0.05 ℃/min, the sweating end point temperature is 37.3 ℃, the constant temperature is kept for 45min at the sweating end point temperature, and the sweat is discharged through the material outlet simultaneously in the sweating process; after sweating was stopped, the temperature of the thermite was increased continuously, and the residual crystals outside the heat exchange tubes were melted and collected, resulting in a final EC product purity of 99.996%.
Example 8
The crystallization purification device shown in fig. 1 is adopted, an overflow weir is arranged above the liquid distributor, and a spiral extension pipe is arranged at the side material outlet and outside the heat exchange pipe. The surface roughness of the outer wall surface of the heat exchange tube is 25. The supporting piece outside the heat exchange tube is a stainless steel sheet layer with the direction of 60 degrees and the downward inclination, and the distance between every two layers is 3 times of the diameter of the device.
Raw materials which comprise 99.07 percent of ethylene carbonate, 0.56 percent of ethylene glycol and 0.37 percent of other EC by weight percentage are preheated and melted, enter from a side material inlet, enter the device through a material inlet and a stretching tube outside the heat exchange tube, and flow downwards along the outer wall surface of the heat exchange tube. The cold agent enters from the cold/hot agent inlet, enters the heat exchange tube through the liquid distributor and the overflow weir above the liquid distributor, and flows downwards along the inner wall surface.
Carrying out program temperature control through an external temperature control system to enable the ethylene carbonate material to naturally crystallize along the outer wall surface of the heat exchange tube, wherein the cooling rate is 0.10 ℃/min, the crystallization end point temperature is 22.5 ℃, and the constant temperature is kept for 45min at the crystallization end point temperature; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, allowing a hot agent to enter from a cold/hot agent inlet, allowing the hot agent to flow downwards along the inner wall surface of the heat exchange tube through an overflow weir, sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature rise rate is 0.05 ℃/min, the sweating end point temperature is 37.3 ℃, the constant temperature is kept for 45min at the sweating end point temperature, and the sweat is discharged through the material outlet simultaneously in the sweating process; after sweating was stopped, the thermite temperature was continued to be raised, and the residual crystals outside the heat exchange tubes were melted and collected, with a final EC product purity of 99.997%.
Example 9
The crystallization purification device shown in fig. 2 is adopted, a conical extension pipe is arranged below the liquid distributor, and a sawtooth-shaped extension pipe is arranged at the side material inlet and outside the heat exchange pipe. The surface roughness of the outer wall surface of the heat exchange tube is 25. The supporting piece outside the heat exchange tube is a single-layer stainless steel wire mesh, and the height of the supporting piece is flush with the liquid level in the device.
Raw materials which comprise 99.51 percent of ethylene carbonate, 0.33 percent of ethylene glycol and 0.16 percent of other EC by weight percent enter from a side material inlet after being preheated and melted, enter the device through the material inlet and a stretching tube outside the heat exchange tube, and flow downwards along the outer wall surface of the heat exchange tube. The refrigerant enters from the cold/hot agent inlet, enters the interior of the heat exchange tube through the liquid distributor and the extension tube below the liquid distributor, and flows downwards along the inner wall surface.
Program temperature control is carried out through an external temperature control system, so that the ethylene carbonate material is naturally crystallized along the outer wall surface of the heat exchange tube, and the cooling rate is 0.15 ℃/min; the method comprises the following steps of (1) keeping an external circulating pump on before the outer wall surface begins to crystallize, enabling ethylene carbonate materials to continuously and slowly flow, turning off the external circulating pump after crystals begin to appear, and then turning on the external circulating pump every 90min for 15 min; keeping the crystallization end point temperature at 25 ℃ and the crystallization end point temperature for 30 min; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, introducing a hot agent from a cold/hot agent inlet, sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature raising rate is 0.10 ℃/min, the sweating end point temperature is 38 ℃, the constant temperature is kept at the sweating end point temperature for 30min, and the sweat is discharged through the material outlet simultaneously in the sweating process; after sweating was stopped, the temperature of the thermite was increased continuously, the residual crystals outside the heat exchange tubes were melted and collected, and the final EC product purity was 99.998%.
Example 10
By adopting the crystallization purification device shown in fig. 2, a zigzag extension tube is arranged below the liquid distributor, as shown in (b) in fig. 3, and an inverted conical extension tube is arranged at the side material inlet and outside the heat exchange tube, as shown in (c) in fig. 3. The surface roughness of the outer wall surface of the heat exchange tube is 25. The supporting piece outside the heat exchange tube is a single-layer stainless steel wire mesh, and the height of the supporting piece is flush with the liquid level in the device.
Raw materials which comprise 99.51 percent of ethylene carbonate, 0.33 percent of ethylene glycol and 0.16 percent of other EC by weight percent enter from a side material inlet after being preheated and melted, enter the device through the material inlet and a stretching tube outside the heat exchange tube, and flow downwards along the outer wall surface of the heat exchange tube. The refrigerant enters from the cold/hot agent inlet, enters the interior of the heat exchange tube through the liquid distributor and the extension tube below the liquid distributor, and flows downwards along the inner wall surface.
Program temperature control is carried out through an external temperature control system, so that the ethylene carbonate material is naturally crystallized along the outer wall surface of the heat exchange tube, and the cooling rate is 0.15 ℃/min; keeping an external circulating pump on in the crystallization process, and continuously and slowly flowing the ethylene carbonate material, wherein the crystallization end point temperature is 25 ℃ and the constant temperature is kept for 30min at the end point temperature; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, introducing a hot agent from a cold/hot agent inlet, and sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature raising rate is 0.10 ℃/min, the sweating end temperature is 38 ℃, the constant temperature is kept at the end temperature for 30min, and the sweat is discharged through the material outlet simultaneously in the sweating process; after sweating was stopped, the temperature of the thermite was increased continuously, the residual crystals outside the heat exchange tubes were melted and collected, and the final EC product purity was 99.998%.
Example 11
The crystallization purification device shown in FIG. 2 is adopted, a spiral extension pipe is arranged below the liquid distributor, and a spiral extension pipe is arranged at the side material inlet and outside the heat exchange pipe. The surface roughness of the outer wall surface of the heat exchange tube is 12.5. The supporting piece outside the heat exchange tube is a plurality of layers of stainless steel wire meshes, and the distance between every two layers is 4 times of the diameter of the device.
Raw materials which comprise 90.15 percent of ethylene carbonate, 6.23 percent of ethylene glycol and 3.62 percent of other EC by weight percentage enter from a side material inlet after being preheated and melted, enter the device through the material inlet and a guide pipe outside the heat exchange pipe, and flow downwards along the outer wall surface of the heat exchange pipe. The refrigerant enters from the cold/hot agent inlet, enters the interior of the heat exchange tube through the liquid distributor and the extension tube below the liquid distributor, and flows downwards along the inner wall surface.
Carrying out program temperature control through an external temperature control system to enable the ethylene carbonate material to naturally crystallize along the outer wall surface of the heat exchange tube, wherein the cooling rate is 0.05 ℃/min; when the temperature of the material in the device reaches 34 ℃, adding a crystal slurry solution of ethylene carbonate from a material inlet through an external circulating pump, wherein the solid weight content is 20%, crystallizing the raw material containing the ethylene carbonate along the outer wall surface of the heat exchange tube, and controlling the supersaturation degree in the crystallization process; the end point temperature of the crystallization process is 15 ℃, and the constant temperature is kept for 60min at the end point temperature; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, introducing a hot agent from a cold/hot agent inlet, sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature raising rate is 0.05 ℃/min, the sweating end point temperature is 36.5 ℃, the constant temperature is kept at the sweating end point temperature for 60min, and the sweat is discharged through the material outlet simultaneously in the sweating process; after sweating was stopped, the thermite temperature was continued to be raised, and the residual crystals outside the heat exchange tubes were melted and collected, with a final EC product purity of 99.994%.
Example 12
By adopting the crystallization purification device shown in fig. 2, a zigzag extension pipe is arranged below the liquid distributor, and as shown in (b) in fig. 3, the zigzag extension pipe is arranged at the side material inlet and outside the heat exchange pipe. The surface roughness of the outer wall surface of the heat exchange tube is 12.5. The supporting piece outside the heat exchange tube is a plurality of layers of stainless steel wire meshes, and the distance between every two layers is 4 times of the diameter of the device.
Raw materials which comprise 99.51 percent of ethylene carbonate, 0.33 percent of ethylene glycol and 0.16 percent of other EC by weight percent enter from a side material inlet after being preheated and melted, enter the device through the material inlet and a stretching tube outside the heat exchange tube, and flow downwards along the outer wall surface of the heat exchange tube. The refrigerant enters from the cold/hot agent inlet, enters the interior of the heat exchange tube through the liquid distributor and the extension tube below the liquid distributor, and flows downwards along the inner wall surface.
Carrying out program temperature control through an external temperature control system to enable the ethylene carbonate material to naturally crystallize along the outer wall surface of the heat exchange tube, wherein the cooling rate is 0.15 ℃/min; when the temperature of the material in the device reaches 36 ℃, adding a crystal slurry solution of ethylene carbonate from a material inlet through an external circulating pump, wherein the solid weight content is 15%, crystallizing the raw material containing the ethylene carbonate along the outer wall surface of the heat exchange tube, and controlling the supersaturation degree in the crystallization process; the final temperature of the crystallization process is 25 ℃, and the temperature is kept constant for 30min at the final temperature; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, introducing a hot agent from a cold/hot agent inlet, sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature raising rate is 0.10 ℃/min, the sweating end point temperature is 38 ℃, the constant temperature is kept at the sweating end point temperature for 30min, and the sweat is discharged through the material outlet simultaneously in the sweating process; after sweating stopped, the temperature of the thermite was increased continuously, and the residual crystals outside the heat exchange tubes were melted and collected, with a final EC product purity of 99.999%.
Comparative example 1
The same raw material composition and process scheme as in example 1 was used, but no weir, extension tube and support were present in the apparatus, and the surface roughness of the outer wall surface of the heat exchange tube was 2.
Raw materials which comprise 90.15 percent of ethylene carbonate, 6.23 percent of ethylene glycol and 3.62 percent of other EC by weight percentage are preheated and melted, and then enter the device from a material inlet, and refrigerant enters the upper seal head from a cold/hot agent inlet and then enters the heat exchange tube through a liquid distributor.
Carrying out program temperature control through an external temperature control system to enable the ethylene carbonate material to naturally crystallize along the outer wall surface of the heat exchange tube, wherein the cooling rate is 0.01 ℃/min, the crystallization end point temperature is 15 ℃, and the constant temperature is kept for 60min at the end point temperature; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, introducing a hot agent from a cold/hot agent inlet, sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature raising rate is 0.01 ℃/min, the sweating end point temperature is 36.5 ℃, the constant temperature is kept at the sweating end point temperature for 40min, and the sweat is discharged through the material outlet simultaneously in the sweating process; after sweating ceased, the thermite temperature was continued to be raised and the residual crystals outside the heat exchange tubes were melted and collected to a final EC product purity of 99.913%.
Comparative example 2
The same raw material composition and process scheme as in example 5 was used, but the apparatus was free of weir, extension tube and support, and the surface roughness of the outer wall surface of the heat exchange tube was 2.
Raw materials which comprise 95.27 percent of ethylene carbonate, 2.93 percent of ethylene glycol and 1.80 percent of other EC by weight percentage are preheated and melted, then enter the device from a material inlet, and refrigerant enters the upper seal head from a cold/hot agent inlet and then enters the heat exchange tube through a liquid distributor.
Carrying out program temperature control through an external temperature control system to enable the ethylene carbonate material to naturally crystallize along the outer wall surface of the heat exchange tube, wherein the cooling rate is 0.05 ℃/min, the crystallization end point temperature is 20 ℃, and the temperature is kept for 60min at the crystallization end point temperature; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, introducing a hot agent from a cold/hot agent inlet, sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature raising rate is 0.025 ℃/min, the sweating end point temperature is 36.8 ℃, the constant temperature is kept at the sweating end point temperature for 30min, and the sweat is discharged through a lower end enclosure and a material outlet simultaneously in the sweating process; after sweating was stopped, the temperature of the thermite was increased continuously, and the residual crystals in the heat exchanger tube were melted and collected, resulting in an EC product purity of 99.926%.
Comparative example 3
The same raw material composition and process scheme as in example 5 was used, but there was no support member in the apparatus, and the surface roughness of the outer wall surface of the heat exchange tube was 2.
Raw materials which comprise 95.27 percent of ethylene carbonate, 2.93 percent of ethylene glycol and 1.80 percent of other EC by weight percentage enter from a material inlet on the side surface after being preheated and melted, enter the device through a material inlet and an inverted cone-shaped extension tube outside the heat exchange tube and flow downwards along the outer wall surface of the heat exchange tube. The cold agent enters from the cold/hot agent inlet, enters the heat exchange tube through the liquid distributor and the overflow weir above the liquid distributor, and flows downwards along the inner wall surface.
Carrying out program temperature control through an external temperature control system to enable the ethylene carbonate material to naturally crystallize along the outer wall surface of the heat exchange tube, wherein the cooling rate is 0.05 ℃/min, the crystallization end point temperature is 20 ℃, and the constant temperature is kept for 60min at the end point temperature; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, introducing a hot agent from a cold/hot agent inlet, sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature raising rate is 0.025 ℃/min, the sweating end point temperature is 36.3 ℃, the constant temperature is kept at the sweating end point temperature for 60min, and the sweat is discharged through a lower end enclosure and a material outlet simultaneously in the sweating process; after sweating was stopped, the temperature of the thermite was increased continuously, and the residual crystals in the heat exchanger tube were melted and collected, resulting in an EC product purity of 99.945%.
Comparative example 4
The same raw material composition and process scheme as in example 1 was used, but no overflow weir or extension tube was included in the apparatus.
Raw materials which comprise 90.15 percent of ethylene carbonate, 6.23 percent of ethylene glycol and 3.62 percent of other EC by weight percentage are preheated and melted, and then enter the device from a material inlet, and refrigerant enters the upper seal head from a cold/hot agent inlet and then enters the heat exchange tube through a liquid distributor.
Carrying out program temperature control through an external temperature control system to enable the ethylene carbonate material to naturally crystallize along the outer wall surface of the heat exchange tube, wherein the cooling rate is 0.01 ℃/min, the crystallization end point temperature is 15 ℃, and the constant temperature is kept for 60min at the end point temperature; after crystallization is stopped, discharging crystallization mother liquor from a material outlet, raising the temperature through an external temperature control system, introducing a hot agent from a cold/hot agent inlet, sweating crystals attached to the outer wall surface of the heat exchange tube, wherein the temperature raising rate is 0.01 ℃/min, the sweating end point temperature is 36.5 ℃, the constant temperature is kept at the sweating end point temperature for 60min, and the sweat is discharged through the material outlet simultaneously in the sweating process; after sweating ceased, the thermite temperature was continued to be raised and the residual crystals outside the heat exchange tubes were melted and collected to a final EC product purity of 99.980%.
It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.
Claims (10)
1. An apparatus for purification by crystallization, comprising:
the device comprises a shell, wherein the top of the shell is provided with a cold/hot agent inlet, the bottom of the shell is provided with a cold/hot agent outlet, two sides of the shell are respectively provided with a material inlet and a material outlet, and the horizontal position of the material inlet is higher than that of the material outlet;
the heat exchange tube and the liquid distributor are arranged in the shell, and the liquid distributor is arranged at the bottom of the shell upper end socket; the top of the heat exchange tube is connected with the liquid distributor, the bottom of the heat exchange tube is connected with the outlet of the cold/hot agent through the lower shell end socket, the outer wall surface of the heat exchange tube has roughness, and meanwhile, the heat exchange tube is provided with a supporting piece.
2. The apparatus of claim 1, wherein the surface roughness of the outer wall surface of the heat exchange tube is 3.2 to 50, preferably 6.3 to 25; and/or the number of the heat exchange tubes is two or more; and/or the device further comprises a nitrogen inlet which is positioned on the side surface of the shell.
3. The apparatus according to claim 1 or 2, wherein the structure of the supporting member provided on the outer wall surface of the heat exchange pipe is net-shaped, rod-shaped or sheet-shaped; preferably, the distance between each layer of the supporting piece is 0.5-5 times of the diameter of the device; more preferably, the distance between each layer of the supporting part is 1-3 times of the diameter of the device.
4. The apparatus according to any one of claims 1 to 3, wherein an overflow weir is arranged above the liquid distributor or an extension pipe is arranged below the liquid distributor, and the extension pipe is positioned in the heat exchange pipe; preferably, the extension pipe arranged below the liquid distributor is in a shape of a cone, a spiral or a sawtooth.
5. The apparatus according to any one of claims 1 to 4, wherein the material inlet and the heat exchange tube are externally provided with extension tubes; preferably, the shape of the extension tube arranged at the material inlet and outside the heat exchange tube is inverted cone, spiral or zigzag.
6. The apparatus according to any one of claims 1 to 5, further comprising an external material circulation pump, an inlet of the external material circulation pump being connected to the material outlet via a pipeline, an outlet of the external material circulation pump being connected to the material inlet via a pipeline; and/or the device further comprises an external temperature control system, wherein an outlet of the external temperature control system is connected with the cold/hot agent inlet through a pipeline, and an inlet of the external temperature control system is connected with the cold/hot agent outlet through a pipeline.
7. A method for the crystallization purification of ethylene carbonate by using the apparatus according to any one of claims 1 to 6, comprising the steps of:
s1, introducing a raw material containing vinyl carbonate into the device through a material inlet of the device, and flowing along the outer wall surface of the heat exchange tube through the material inlet and an extension tube arranged outside the heat exchange tube;
s2, introducing a refrigerant into the device through a cold/hot agent inlet, distributing the refrigerant through a liquid distributor, then entering the heat exchange tube along an overflow weir arranged above the liquid distributor or an extension tube arranged below the liquid distributor, flowing along the inner wall surface of the heat exchange tube, controlling the temperature through an external temperature control system, crystallizing the ethylene carbonate in the raw material on the outer wall of the heat exchange tube, and discharging crystallization mother liquor after crystallization is finished;
s3, introducing a hot agent into the device through the cold/hot agent inlet, after the hot agent is distributed by the liquid distributor, entering the heat exchange tube along an overflow weir arranged above the liquid distributor or an extension tube arranged below the liquid distributor, flowing along the inner wall surface of the heat exchange tube, controlling the temperature through an external temperature control system, sweating the crystal on the outer wall of the heat exchange tube, discharging sweat from the material outlet of the device, wherein the residual crystal on the outer wall of the heat exchange tube is the purified ethylene carbonate product.
8. The method according to claim 7, wherein the temperature reduction rate in the crystallization process is 0.01-0.15 ℃/min, the crystallization end point temperature is 15-25 ℃, and the constant temperature time at the crystallization end point temperature is not less than 30 min; and/or the presence of a gas in the gas,
the temperature rise rate in the sweating process is 0.01-0.1 ℃/min, the sweating end point temperature is 36.5-38 ℃, and the constant temperature time of the sweating end point temperature is not less than 30 min.
9. The method according to claim 7 or 8, wherein the formation of crystals during crystallization is natural crystallization or crystallization is initiated by adding seed crystals; preferably, the seed crystal is a crystal slurry solution of ethylene carbonate with the solid weight content not higher than 20%; further preferably, the adding temperature of the seed crystal is 34-36 ℃.
10. The method according to any one of claims 7 to 9, wherein the external material circulation pump is intermittently turned on or continuously turned on during the crystallization process; and/or the process is carried out under nitrogen seal; and/or the weight content of the ethylene carbonate in the raw material containing the ethylene carbonate is more than or equal to 90 percent.
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